content: /*
   * Copyright 2017 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package hu.akarnokd.reactive4javaflow.impl.operators;
  
  import hu.akarnokd.reactive4javaflow.*;
  import hu.akarnokd.reactive4javaflow.fused.ConditionalSubscriber;
  import hu.akarnokd.reactive4javaflow.impl.SubscriptionArbiter;
  
  import java.util.concurrent.Flow;
  
  public final class FolyamSwitchIfEmpty<T> extends Folyam<T> {
  
      final Folyam<T> source;
  
      final Flow.Publisher<? extends T> other;
  
      public FolyamSwitchIfEmpty(Folyam<T> source, Flow.Publisher<? extends T> other) {
          this.source = source;
          this.other = other;
      }
  
      @Override
      protected void subscribeActual(FolyamSubscriber<? super T> s) {
          if (s instanceof ConditionalSubscriber) {
              source.subscribe(new SwitchIfEmptyConditionalSubscriber<>((ConditionalSubscriber<? super T>)s, other));
          } else {
              source.subscribe(new SwitchIfEmptySubscriber<>(s, other));
          }
      }
  
      static final class SwitchIfEmptySubscriber<T> extends SubscriptionArbiter implements FolyamSubscriber<T> {
  
          final FolyamSubscriber<? super T> actual;
  
          Flow.Publisher<? extends T> other;
  
          boolean once;
  
          SwitchIfEmptySubscriber(FolyamSubscriber<? super T> actual, Flow.Publisher<? extends T> other) {
              this.actual = actual;
              this.other = other;
          }
  
          @Override
          public void onSubscribe(Flow.Subscription subscription) {
              arbiterReplace(subscription);
              if (!once) {
                  actual.onSubscribe(this);
              }
          }
  
          @Override
          public void onNext(T item) {
              if (!once) {
                  once = true;
              }
              actual.onNext(item);
          }
  
          @Override
          public void onError(Throwable throwable) {
              actual.onError(throwable);
          }
  
          @Override
          public void onComplete() {
              if (once) {
                  actual.onComplete();
              } else {
                  once = true;
                  Flow.Publisher<? extends T> p = this.other;
                  other = null;
                  p.subscribe(this);
              }
          }
      }
  
      static final class SwitchIfEmptyConditionalSubscriber<T> extends SubscriptionArbiter implements ConditionalSubscriber<T> {
  
          final ConditionalSubscriber<? super T> actual;
  
          Flow.Publisher<? extends T> other;
  
          boolean once;
  
          SwitchIfEmptyConditionalSubscriber(ConditionalSubscriber<? super T> actual, Flow.Publisher<? extends T> other) {
              this.actual = actual;
              this.other = other;
          }
  
          @Override
          public void onSubscribe(Flow.Subscription subscription) {
              arbiterReplace(subscription);
              if (!once) {
                  actual.onSubscribe(this);
              }
          }
  
          @Override
          public void onNext(T item) {
              if (!once) {
                  once = true;
              }
              actual.onNext(item);
          }
  
          @Override
          public boolean tryOnNext(T item) {
              if (!once) {
                  once = true;
              }
              return actual.tryOnNext(item);
          }
  
          @Override
          public void onError(Throwable throwable) {
              actual.onError(throwable);
          }
  
          @Override
          public void onComplete() {
              if (once) {
                  actual.onComplete();
              } else {
                  once = true;
                  Flow.Publisher<? extends T> p = this.other;
                  other = null;
                  p.subscribe(this);
              }
          }
      }
  }
  